The present disclosure relates to a gas turbine engine and, more particularly, to an optical tip-timing probe system therefor.
Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section for burning a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases.
Beam Interrupt probes for optical tip-timing typically require two (2) “periscope” probes per channel. Arrangements that involve protrusion of the end of the “periscope” into the flow passage may not be desirable because exposure to the full effects of the hot compressed gases. To minimize the protrusion, the periscope may be designed to “look” obliquely into the flow passage. However, such an arrangement has the disadvantage that the probe's field of view may be undesirably limited and cannot readily be altered significantly because such alteration requires modification to the engine structure.
Furthermore, “Periscope” probes may disturb the aerodynamic behavior in the gas-path thereby driving additional (non-production related) vibration in rotating hardware. For this reason the use of “periscope” Beam Interrupt probes in the high pressure compressor (HPC)—particularly the aft stages—has been abandoned, despite the advantages inherent in a Beam Interrupt probes' dual measurement over a traditional spot probe's single measurement capability.